Thursday, May 14, 2009

Harmful Effects of Antioxidant Supplements on Athletes?

As a scientist, one of my hobbies is to peruse the articles on exercise physiology. I came across one published this week in PNAS ( by Ristow et al, which I simply can't resist discussing.

I've always been a bit skeptical of "performance-enhancing" supplements. Afterall, they are not FDA-approved and oftentimes, very little is disclosed about what's in them. I don't like putting unknown, unproven things in my body. A lot of triathletes nowadays are scarfing antioxidant supplements because antioxidants are bad, right? Well, maybe, maybe not. Turns out, some are bad, whereas others may be good. Exercise is good for you (duh)--increases insulin sensitivity, metabolism, burns fat, promotes muscle anabolism (and all that goes along with that e.g. mitochonidria production). However, it is a well-known fact that exercise increases production of oxidants (free radicals) by MUSCLE. Hey, wait a minute, I thought free radicals were bad (they have been shown to damage cells and speed up the aging process)! Right? Right? A commonly-held belief amongst the masses were that these exercise-induced free radicals had negative effects on the body and delayed recovery. In response, the supplement fairies manufactured large gobs of "antioxidant supplements" (mainly enormous doses of oxidant-scavenging C and E vitamins).

In this study, insulin sensitivity, glucose metabolism and production of the body's natural antioxidants were measured in trained and untrained subjects taking either placebo or antioxidant supplement (C & E vitamins). Antioxidants supplementation was found to prevent the enhanced insulin sensitivity and boost in the body's oxidant defenses normally afforded by exercise. In addition, production of beneficial mediators of insulin sensitivity (PPAR-gamma and PGC-1) and antioxidant defense (superoxide dismutase and glutathione peroxidase) were inhibited (these are normally boosted in response to exercise).

Turns out that the free radicals produced in response to exercise may actually be used by the body to increase metabolism and enhance insulin sensitivity. So, sometimes free radicals are the good guys? Perhaps. At the very least, maybe we should think twice before popping the expensive supplements!

--Ristow et al (2009)


Backpacker said...

I'm over the whole supplement/vitamin/performance enhancing trend. Remember when chromium was hot? A freaking metal they put on cars? Weird. Every study is basically saying a balanced diet is as good as any pill. I'm not taking anything but an occasional fish oil supplement and occasional vitamin D (which itself is quite trendy) and I'm having my best season ever.

I love your science-y posts.

Grey Beard said...

Based on very limited personal trials, I have found Acai Berry added to my Gatorade to be helpful. Any science on that? It seems to speed digestion of ride fuels and makes them burn very cleanly (no gas, bloating, GI fouling, increases max carb digestion by perhaps 30-40%), and is a product with a long history of human consumption.

By contrast, I have been in a running debate with a friend RE: the benefits and risks of carnosine - used in Hammer HEED and Perpetuem - and wondered if you had any science on the safety of this compound? The maltodextrin I'm cool with, and its users swear by it, (of course) but the carnosine just looks like it's from the Area 51 of nutrition to me.

Being an unapologetic egg-head, I feel quite privileged that you share the benefit of your excellent credentials with me. Thank you >:D<

Now about that eating off the top of your stomach every 2 hours thing.... :D~

Grey Beard said...

It's not every day someone cites something from err...


... reminds me of the monster truck I saw one day with a license plate frame that wryly spelled out "litl pp" :D

Wes said...

Good stuff. I quit smoking for the same reason. Stop sticking non-natural stuff in my mouth, beer excepted of course ;-)

Benson said...

Good information.
I have also paired down to only the occasional multivitamin to fill in the gaps.

Cliff said...

Hey Rachel,

I read the same thing this morning. Hold and behold, I always get my vitamins from natural food. Like veges and fruits and all that good stuff. I think as we enter a pill popping nation, we need to be more aware we just cannot squeeze some vitmains into a pill and consider that as healthy.

U said...

I have been racing and training for a few years, i have been taking fish oil, flax seed oil, and borage seed oil,
along with a multivitamin, a good diet and lots of water !